This invention relates to band saws and more particularly to the control of speed of material being fed to a band saw to achieve optimum cutting operation.
Systems have been proposed heretofore for controlling the speed of material through a band saw. U.S. Pat. No. 4,926,917 discloses the use of two saw line light lines, one at the entrance end of a log and the other at the exit end on the opposite side of the log, to determine the thickness of the log, and a microprocessor produces an electric signal for controlling the speed of feed of the log through the band saw. A transducer is employed to measure lateral deflection of the saw blade as an indication to an operator of dull saw teeth or other problem with the blade.
In U.S. Pat. No. 5,694,821 the depth of cut measurement is similar to that disclosed in the patent discussed above, an electromagnetic proximity sensor detects lateral deflection of a band saw blade and the electric signal is processed to provide a corresponding electric drive motor signal to increase or decrease the speed of a log being moved through the band saw.
Both of the systems disclosed above utilize measurement methods of limited accuracy and therefore the precision of log feed rate and deviation resolution are less than desired.
The band saw feed speed system of this invention utilizes a first laser light line to provide a three dimensional reference for the depth of cut measurement, a second laser light line to provide a three dimensional reference for saw blade deviation measurement, and a video camera to provide a view of the full range of log diameters and of the laser light projections and to supply measurement data to a microprocessor which controls the variable drive motor of a saw mill log transport mechanism according to the variations in depth of cut being made by a band saw blade and according to variations in lateral deviation of the band saw blade.
It is the principal objective of this invention to provide a band saw feed speed system that overcomes the aforementioned limitations of prior band saw feed speed systems.
Another objective of this invention is to provide a band saw feed speed system of the class described in which the detection of band saw blade deviation provides a more direct measurement and correspondingly increased precision of deviation measurements.
A further objective of this invention is the provision of a band saw feed speed system of the class described in which the measurements of depth of cut and lateral band saw blade deviation are made with precision laser beams and a video camera communicating with a microprocessor for controlling the speed of the drive motor of the log transport mechanism.
The foregoing and other objects and advantages of this invention will appear from the following detailed description, taken in connection with the accompanying drawings of a preferred embodiment.